defense secretary leon panetta ordered a pentagon investigation on monday involving one of the u.s. military's biggest names. general john allen, the man who succeeded david petraeus as head of the international forces in afghanistan, is now linked to the fbi investigation involving his predecessor. >> i want to thank you all so much for being here this morning. >> reporter: secretary of defense leon panetta confirms department of defense is investigating allen, and a senior u.s. defense official says the inquiry centers around potentially inappropriate e-mails with jill kelly, the florida woman who sparked an investigation that led to petraeus's resignation as head of the cia. >> if you know my sister, like i said, she is a dedicated mother and a dedicated wife. >> reporter: kelly first went to the fbi when she received threatening e-mails from an anonymous source. those were allegedly linked to paula broadwell. broadwell was having an affair with petraeus and reportedly believed kelly was a romantic rival for his attention. monday night, fbi investigators were in broadwell's charl